The object of this research is to understand the mechanism by which mammalian cells regulate the expression of genetic information. We have identified several genetically determined quantitative variants affecting the enzymes beta-galactosidase and amylase. We have also developed methods for measurement of the in vivo concentration, synthesis, and degradation of the enzymes. Our aim is to determine the chromosomal location and molecular mechanism by which these genetic mutants alter the normal enzyme level. If we can understand how normal enzyme concentration is altered by mutation, the regulatory mechanisms responsible for maintenance of steady-state enzyme levels may be identified.